At the base level, the CLS 550 scores a respectable 18 mpg city, 27 mpg highway, and 21 mpg combined, while generating 402 horsepower from a twin-turbo V-8 engine. Adding 4Matic all-wheel drive brings those figures down to 18/25/20 mpg. Eco stop-start is now standard on both CLS 550 variants.
The fiercely fast CLS63 AMG makes 550 horsepower and turns it into 16/22/18 mpg. The new higher-performance CLS63 AMG S steps up the power even further, but manages the same gas mileage ratings--and both AMG versions include standard all-wheel drive.